Blender 2.8 no shadow lighting
There is no global solution if you are using an environment texture in your world material. 
You can turn off shadows per object/lamp though. 
For rendered objects go into the object settings under cycles visibility turn off Shadow.
For lamps go into the material settings and turn off Cast Shadow.
You can do that with multiple objects, select them all and hold ALT while disabling the shadow option. If your objects have mixed settings for this parameter toggle it twice, to unify them.